Microbial reduction of selenate and nitrate: common themes and variations

2005 ◽  
Vol 33 (1) ◽  
pp. 173-175 ◽  
Author(s):  
C.A. Watts ◽  
H. Ridley ◽  
E.J. Dridge ◽  
J.T. Leaver ◽  
A.J. Reilly ◽  
...  
Keyword(s):  
Nitrate Reductase ◽  
Active Site ◽  
Early Stage ◽  
Microbial Reduction ◽  
Water Soluble ◽  
The Other ◽  
Enzyme Systems ◽  
The Common ◽  
Insight Into ◽  
Respiratory Nitrate Reductase

A number of biochemically distinct systems have been characterized for the microbial reduction of the oxyanions, selenate (SeO42−) and nitrate (NO3−). Two classes of molybdenum-dependent nitrate reductase catalyse the respiratory-linked reduction of nitrate (NO3−) to nitrite (NO2−). The main respiratory nitrate reductase (NAR) is membrane-anchored, with its active site facing the cytoplasmic compartment. The other enzyme (NAP) is water-soluble and located in the periplasm. In recent years, our understanding of each of these enzyme systems has increased significantly. The crystal structures of both NAR and NAP have now been solved and they provide new insight into the structure, function and evolution of these respiratory complexes. In contrast, our understanding of microbial selenate (SeO42−) reduction and respiration is at an early stage; however, similarities to the nitrate reductase systems are emerging. This review will consider some of the common themes and variations between the different classes of nitrate and selenate reductases.

Studies on the Toxicity of Aromatic Hydrocarbons on Chorella Vulgaris by 3D-QSAR Using CoMFA and CoMSIA Methods

2012 ◽  
Vol 610-613 ◽  
pp. 3574-3579
Author(s):  
Cui Hua Wang ◽  
Sheng Long Yang ◽  
Chao Lu ◽  
Hong Xia Yu ◽  
Lian Shen Wang ◽  
...  
Keyword(s):  
Benzene Ring ◽  
Aromatic Hydrocarbons ◽  
Common Factor ◽  
3D Qsar ◽  
The Other ◽  
Contour Maps ◽  
Substituent Group ◽  
Donor And Acceptor ◽  
The Common ◽  
Insight Into

By using CoMFA and CoMSIA methods, the new quantitative structures of 25 aromatic hydrocarbons and the 96 hr-EC50 data with C. vulgaris have been investigated to obtain more detailed insight into the relationships between molecular structure and bioactivity. Compared to CoMFA (the average Q2LOO option =0.610), CoMSIA (the average Q2LOO =0.736) has the better results with robustness and stability. CoMSIA analysis using steric, electrostatic, hydrophobic, and H-bond donor and acceptor descriptors show H-bond donor is the common factor for influencing the toxicity, the steric and electrostatic descriptors are next and the hydrophobic descriptor was last. From the contour maps, the number of benzene ring is more crucial for the compound toxicity and the compounds with more benzene ring make toxicity increased. Under the same number of benzene ring, the kind of substituent group and the formed ability of H-bond are the other parameters to influencing the aromatic hydrocarbons toxicity.

scholarly journals Kinetic probes for inter-domain co-operation in human somatic angiotensin-converting enzyme

2005 ◽  
Vol 391 (3) ◽  
pp. 641-647 ◽  
Author(s):  
Olga E. Skirgello ◽  
Peter V. Binevski ◽  
Vladimir F. Pozdnev ◽  
Olga A. Kost
Keyword(s):  
Angiotensin Converting Enzyme ◽  
Enzymatic Activity ◽  
Active Site ◽  
The Other ◽  
Converting Enzyme ◽  
Human Enzyme ◽  
Independent Functions ◽  
The Common ◽  
The Individual ◽  
Hydrolysis Of

s-ACE (the somatic form of angiotensin-converting enzyme) consists of two homologous domains (N- and C-domains), each bearing a catalytic site. Negative co-operativity between the two domains has been demonstrated for cow and pig ACEs. However, for the human enzyme there are conflicting reports in the literature: some suggest possible negative co-operativity between the domains, whereas others indicate independent functions of the domains within s-ACE. We demonstrate here that a 1:1 stoichiometry for the binding of the common ACE inhibitors, captopril and lisinopril, to human s-ACE is enough to abolish enzymatic activity towards FA {N-[3-(2-furyl)acryloyl]}-Phe-GlyGly, Cbz (benzyloxycarbonyl)-Phe-His-Leu or Hip (N-benzoylglycyl)-His-Leu. The kinetic parameters for the hydrolysis of seven tripeptide substrates by human s-ACE appeared to represent average values for parameters obtained for the individual N- and C-domains. Kinetic analysis of the simultaneous hydrolysis of two substrates, Hip-His-Leu (S1) and Cbz-Phe-His-Leu (S2), with a common product (His-Leu) by s-ACE at different values for the ratio of the initial concentrations of these substrates (i.e. σ=[S2]0/[S1]0) demonstrated competition of these substrates for binding to the s-ACE molecule, i.e. binding of a substrate at one active site makes the other site unavailable for either the same or a different substrate. Thus the two domains within human s-ACE exhibit strong negative co-operativity upon binding of common inhibitors and in the hydrolysis reactions of tripeptide substrates.

The Reception Process in Austria and Switzerland

2008 ◽  
Author(s):  
Daniela Thurnherr
Keyword(s):  
Human Rights ◽  
Early Stage ◽  
Case Law ◽  
Legal Order ◽  
The Other ◽  
Council Of Europe ◽  
Starting Position ◽  
European Court ◽  
The Status ◽  
The Common

This chapter discusses the reception of the ECHR in Austria and Switzerland. Topics covered include the accession and ratification of the ECHR in both countries, the status of the ECHR in national law, an overview of the activity of the European Court of Human Rights, and the ECtHR's case law and its effects on the national legal order. Although both countries joined the ECHR at a relatively early stage, this starting position led to different outcomes. The main reason is because the common denominators of neutrality and federalism in these two countries are actually rather small: as Austria follows a very different concept of neutrality, it did not face any (political) difficulties before and during the ratification process. Switzerland, on the other hand, was very reluctant to join the Council of Europe and careful to avoid any concessions with regard to neutrality.

scholarly journals Beetle luciferases with naturally red- and blue-shifted emission

2018 ◽  
Vol 1 (4) ◽  
pp. e201800072 ◽  
Author(s):  
César Carrasco-López ◽  
Juliana C Ferreira ◽  
Nathan M Lui ◽  
Stefan Schramm ◽  
Romain Berraud-Pache ◽  
...  
Keyword(s):  
Active Site ◽  
Computational Studies ◽  
Reaction Sequence ◽  
Yellow Light ◽  
Conformational Landscape ◽  
The Common ◽  
Molecular Origin ◽  
Site Mutagenesis ◽  
Computational Analyses ◽  
Insight Into

The different colors of light emitted by bioluminescent beetles that use an identical substrate and chemiexcitation reaction sequence to generate light remain a challenging and controversial mechanistic conundrum. The crystal structures of two beetle luciferases with red- and blue-shifted light relative to the green yellow light of the common firefly species provide direct insight into the molecular origin of the bioluminescence color. The structure of a blue-shifted green-emitting luciferase from the firefly Amydetes vivianii is monomeric with a structural fold similar to the previously reported firefly luciferases. The only known naturally red-emitting luciferase from the glow-worm Phrixothrix hirtus exists as tetramers and octamers. Structural and computational analyses reveal varying aperture between the two domains enclosing the active site. Mutagenesis analysis identified two conserved loops that contribute to the color of the emitted light. These results are expected to advance comparative computational studies into the conformational landscape of the luciferase reaction sequence.

Reaction of threonine synthase with the substrate analogue 2-amino-5-phosphonopentanoate: implications into the proton transfer at the active site

2019 ◽  
Vol 167 (4) ◽  
pp. 357-364
Author(s):  
Yasuhiro Machida ◽  
Takeshi Murakawa ◽  
Akiko Sakai ◽  
Mitsuo Shoji ◽  
Yasuteru Shigeta ◽  
...  
Keyword(s):  
Catalytic Reaction ◽  
Active Site ◽  
Catalytic Mechanism ◽  
The Other ◽  
Amino Group ◽  
Threonine Synthase ◽  
Spectral Changes ◽  
Proton Migration ◽  
Insight Into

Abstract Threonine synthase catalyses the conversion of O-phospho-l-homoserine and a water molecule to l-threonine and has the most complex catalytic mechanism among the pyridoxal 5′-phosphate-dependent enzymes. In order to study the less-characterized earlier stage of the catalytic reaction, we studied the reaction of threonine synthase with 2-amino-5-phosphonopentanoate, which stops the catalytic reaction at the enamine intermediate. The global kinetic analysis of the triphasic spectral changes showed that, in addition to the theoretically expected pathway, the carbanion is rapidly reprotonated at Cα to form an aldimine distinct from the external aldimine directly formed from the Michaelis complex. The Kd for the binding of inhibitor to the enzyme decreased with increasing pH, showing that the 2-amino-group-unprotonated form of the ligand binds to the enzyme. On the other hand, the rate constants for the proton migration steps within the active site are independent of the solvent pH, indicating that protons are shared by the active dissociative groups and are not exchanged with the solvent during the course of catalysis. This gives an insight into the role of the phosphate group of the substrate, which may increase the basicity of the ε-amino group of the catalytic lysine residue in the active site.

Religious-Cultural Identity in Thrace and Moesia Inferior

2005 ◽  
Author(s):  
Ulrike Peter
Keyword(s):  
Cultural Identity ◽  
The Other ◽  
Female Figure ◽  
Philip Ii ◽  
Good Insight ◽  
Special Regard ◽  
The Common ◽  
Common Identity ◽  
The City ◽  
Insight Into

The Beauty and Attractions of Philippopolis, named after Philip II, king of Macedonia, praised in this poetical manner by Lucian, were also celebrated on its coinage in Roman times. Hence the river Hebrus, navigable up to Philippopolis in antiquity, was often depicted on coins; on Hadrianic coins it was even named (pl. 8.1, 1). Its great importance for the city is further reflected in the common illustrations of the river-god and the city-goddess (pl. 8.1, 2). And one coin with the river-god also shows other sources of wealth for the city: little genii are depicted representing agriculture and mining (pl. 8.1, 3). While the AIMOΣ, depicted only on coins of Nicopolis ad Istrum, is shown as a male personification (in the form of a young hunter), the smaller mountains of Rhodope, situated near Philippopolis, are depicted as a charming female figure with an explanatory legend (ROΔOΠH) on coins of Philippopolis (pl. 8.1, 4). In addition, the three hills which formed the acropolis of the city (which, as a consequence, was called Trimontium in Roman times), and are known today as Nebet-, Džambaz-, and Taximtepe, were depicted (singly or all together) on coins of Philippopolis (pl. 8.1, 5). Sometimes even the other hills of the city (which are said to have been seven in all) can be seen on the coins. So a statue of Heracles, situated on a hill, supposedly represented the second highest elevation of the city, the Bundardžika (pl. 8.1, 6). The pictures of these hills are combined with appropriate buildings—temples, statues, aqueducts— on the coins (pl. 8.1, 7). It is clear that such illustrations conveyed a specific image of the city and the landscape, and were intended to show essential aspects of the common identity of the Philippopolites. As a consequence they give a good insight into the processes of acculturation which led to the formation or change of identities. They show how indigenous, local, or regional traditions, myths, and stories of origins were conserved or changed. They also inform us about the adaptation of foreign influences (for example, the taking over and/or integration of foreign deities in the local pantheon) or the resistance against such influences. Such central aspects of ‘Coinage and Identity’ will be studied in detail in this chapter, with special regard to Thrace and Moesia Inferior.

scholarly journals The Commons: Three Case Studies of Community Forested Land

2016 ◽  
Vol 2 (1) ◽  
pp. 1
Author(s):  
Ruth B. McKay
Keyword(s):  
Case Studies ◽  
Natural Habitat ◽  
The Other ◽  
Community Design ◽  
Private Ownership ◽  
The Third ◽  
The Commons ◽  
The Common ◽  
Common Lands ◽  
Insight Into

<p>This paper examines three communities that include common land in the community design. The common land provides natural habitat for recreational purposes along with privacy and a natural visual barrier. One of the three communities the commons arrangement fails after more than thirty years and the community sells most of the common land for private ownership. The other two are examples of successful commons where the community maintains the common lands and exhibits a growing commitment to the holding of common land. The paper examines why two of the three communities have success and prosper while the third fails. The findings provide insight into designs that work to maintain community common land and those that fail. </p>

Neuromuscular properties of the quintuply innervated flexor muscle in lobster limbs

1991 ◽  
Vol 69 (2) ◽  
pp. 477-488 ◽  
Author(s):  
T. J. Wiens ◽  
Joanne Pearce ◽  
C. K. Govind
Keyword(s):  
Active Site ◽  
Oxidative Capacity ◽  
The Other ◽  
Muscle Fibres ◽  
Flexor Muscle ◽  
Electron Microscopic ◽  
Leg Muscles ◽  
Synaptic Interactions ◽  
The Common ◽  
To Receive

The flexor muscle of the lobster's walking leg was shown by enzyme histochemistry and electrophysiology to display a regional segregation of fibre types: medial fibres have a higher ATPase activity, lower oxidative capacity, and shorter membrane time constant than peripheral fibres lying near the cuticle. The muscle was confirmed to receive one inhibitory and four excitatory motor axons. As judged by the properties of their output excitatory junctional potentials (ejp's), the four excitors lie along the fast-to-slow gradient defined by the two specialized excitors of dually excited muscles. The Fα axon produces initially large ejp's which facilitate weakly or antifacilitate; they are similar to those of fast axons in other muscles. The Fρ axon at the other end of the spectrum produces strongly facilitating ejp's which are initially small, resembling those of known slow axons. The Fβ and Fγ axons show intermediate properties. The inhibitor, which is the common inhibitor of all leg muscles, innervates preferentially the more tonic muscle fibres, as does Fρ. Muscle fibres were observed to receive anywhere from one to five efferents, most receiving two to four. Serial electron microscopic observations in several regions revealed a rich supply of synaptic terminals, usually comprising a single inhibitory terminal and two or three excitatory ones. The inhibitory terminal typically has a few large synapses, each with more than one active site. Excitatory terminals, on the other hand, have many more smaller synapses, each with at least one active site. Although excitatory and inhibitory terminals were often closely juxtaposed, no synaptic interactions were observed between them.

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